Caxy Diver,
Tuffy Rocks? Tuffy Canyon? The dive sites - as labeled on the Ambergris Caye dive sites map - are not consistent. Where is the "Tuffy" dive site you referred to? On one map, it is labeled Tuffy Canyon and is located south of Tackle Box. On another website, it is called Tuffy Rocks and is described as being "adjacent to Tackle Box."
The names of sites vary over the years, though the actual sites don't much. "Tuffy" is used nowadays to refer to two separate locations - a dive site outside the reef near the main "San Pedro" cut in the reef, with the mooring buoy held in around 50ft and the descent through the "spur and Groove" formations to the abyss is pretty close (not much swimming involved); and the site that Caxy Diver referred to which is a very shallow location just inside the reef by the same cut.
The latter is generally known as "inside Tuffy" or "Coliseum". It's very shallow (you're struggling to find 20ft, and much of it is less than half that) but it's very pretty with lots of elkhorn coral and little coloured fishes (you can tell I'm not a naturalist!). In calm sea conditions, and it's pretty sheltered there, it's lovely to snorkel or do a shallow dive. Although it's shallow, there are few places where you can stand up so it's not ideal for early scuba training. And of course, buoyancy control is a challenge in such shallow water. But it's not much frequented and is a lovely spot, very accessible from shore.
"Tuffy" proper is one of my favourite sites here in San Pedro, as there's a large sandy area suitable for training; around the edge of that area in suitable conditions makes for a wonderful night dive - there are always octopii to be seen there, and if you haven't seen an octopus at night your diving has been severely limited; and it's a site which is close to the drop off and ideal for advanced dives. When the sea has been rough the visibility there does deteriorate more than at some other sites though, because of the nearby cut/channel.
I often read that people think that all the good diving in Belize is at the atolls. The diving there is certainly good, but we have superb and fascinating diving right next to our island. Anyone who thinks diving on the barrier reef here is boring or "average" hasn't been shown it properly!